4.12.0-rc6+: WQ_MEM_RECLAIM hci0:hci_power_off is flushing !WQ_MEM_RECLAIM events:btusb_work

[Dominik Brodowski]

Hi!

On my Dell XPS 13 9343 (x86_64), the following warning was logged right
after a resume from suspend-to-mem (not on *every* resume, though, so it
might be hard to reproduce). The kernel is v4.12.0-rc6+ as of 94a6df251dd0,
and I don't really use bluetooth, though the drivers are loaded:

PM: Finishing wakeup.
OOM killer enabled.
Restarting tasks ... done.
Bluetooth: hci0: read Intel version: 370710018002030d00
Bluetooth: hci0: Intel Bluetooth firmware file: intel/ibt-hw-37.7.10-fw-1.80.2.3.d.bseq
Bluetooth: hci0: Intel Bluetooth firmware patch completed and activated
... <more, unrelated messages>
workqueue: WQ_MEM_RECLAIM hci0:hci_power_off is flushing !WQ_MEM_RECLAIM events:btusb_work
------------[ cut here ]------------
WARNING: CPU: 2 PID: 14231 at /home/brodo/local/kernel/git/linux/kernel/workqueue.c:2423 check_flush_dependency+0xb3/0x100
Modules linked in:
CPU: 2 PID: 14231 Comm: kworker/u9:4 Not tainted 4.12.0-rc6+ #3
Hardware name: Dell Inc. XPS 13 9343/0TM99H, BIOS A11 12/08/2016
Workqueue: hci0 hci_power_off
task: ffff9432dad58000 task.stack: ffff986d43790000
RIP: 0010:check_flush_dependency+0xb3/0x100
RSP: 0018:ffff986d43793c90 EFLAGS: 00010086
RAX: 000000000000005a RBX: ffff943316810820 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000096 RDI: 0000000000000001
RBP: ffff986d43793cb0 R08: 0000000000000775 R09: ffffffff85bdd5c0
R10: 0000000000000040 R11: 0000000000000000 R12: ffffffff84d596e0
R13: ffff9432dad58000 R14: ffff94321c640320 R15: ffff9432dad58000
FS:  0000000000000000(0000) GS:ffff94331f500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007b8bca242000 CR3: 000000014f60a000 CR4: 00000000003406e0
Call Trace:
 flush_work+0x8a/0x1c0
 ? flush_work+0x184/0x1c0
 ? skb_free_head+0x21/0x30
 __cancel_work_timer+0x124/0x1b0
 ? hci_dev_do_close+0x2a4/0x4d0
 cancel_work_sync+0x10/0x20
 btusb_close+0x23/0x100
 hci_dev_do_close+0x2ca/0x4d0
 hci_power_off+0x1e/0x50
 process_one_work+0x184/0x3e0
 worker_thread+0x4a/0x3a0
 ? preempt_count_sub+0x9b/0x100
 ? preempt_count_sub+0x9b/0x100
 kthread+0x125/0x140
 ? process_one_work+0x3e0/0x3e0
 ? __kthread_create_on_node+0x1a0/0x1a0
 ? do_syscall_64+0x58/0xd0
 ret_from_fork+0x27/0x40
Code: 00 75 bf 49 8b 56 18 48 8d 8b b0 00 00 00 48 81 c6 b0 00 00 00 4d 89 e0 48 c7 c7 20 23 6b 85 c6 05 83 cd 31 01 01 e8 bf c4 0c 00 <0f> ff eb 93 80 3d 74 cd 31 01 00 75 a5 65 48 8b 04 25 00 c5 00 
---[ end trace b88fd2f77754bfec ]---


Best
	Dominik